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Trick equipotential bonding

I’m faced with a really tricky one and I might have to walk away.

went to an EVSE quote today and it’s a classic case of oh dear they built over the top of it! So the property has an external gas meter, 10mm bond at the meter but the metallic gas pipe then goes under ground (paved drive) before entering the house after the point at which it is bonded. Indoors the whole place is tiled or laminate floors, there must be a T in the gas pipe somewhere under there because it appears straight out a wall behind the cooker and weirdly down from the ceiling above the boiler. Getting a bond over to either is not something that is likely to be acceptable to the client. I remember reading a code of practice a nice plumber/gas safe engineer showed me once that stated that where the meter is external and the customer side of the service goes underground again before entering the property that the bond should ideally be located internally 600mm from its reemergence rather than within 600mm of the meter.

personally I’ve always preferred an internal bond with external meters, mostly because I’ve found so many corroded ones outside, but…As it’s not practical to do that without destroying a newly tiled floor to run the cable under, can I say that this is not ideal but is still compliant as there is an external bond within 600mm of the meter, all be it before an earth potential is reintroduced? I’m not entirely sure it would have the desired effect as it is.

They’ve also had their earth electrode paved over, which begs the question why budding young builders on the city and guilds don’t get better training on some basic electrical awareness, in fact considering how laughably easy the PartP exam is, surely it’s more appropriate for other trades to do it than sparkies? Because let’s face it, it’s not us going around paving over earth pins or boxing in the stopcock now is it?

rant over

Parents
  • Not sure that all the builders actually pass the C and G to be honest. Forget basic electrics, what about water... I've just had a chap build me a workshop where the felt roof tucked neatly behind the Fascia instead of curling over in front of it into the gutter, so the water would be ducted indoors, and the gutter stays more or less empty. And flat roofs are not supposed to be truly flat !!. If I'd really wanted to come home and spend a weekend cursing and redoing it I'd not have employed someone who claimed some expertise in the first place. So maybe you expect  bit much from the average driveway paver as there are truly some total muppets out there.

    Anyway, to your point, are you saying there is a bond wire already but the route is unknown, or that it is not connected anywhere ? A long wander lead  test will probably tell you. Given that the resistance of metal pipe is lower per metre than the cable we bond with (22mm dia copper tube is about 60mm2 equivalent copper area) the idea that the bond not being within 60cm is actually a problem is not really true, more of an ease of  inspection issue than an electrical one unless the pipe has an insulating  break in it.

    Is this a TT house then or a TNx with augmenting electrode ?

    If the former it sounds EVSE ideal if the latter may be an O-PEN box rather than too much digging or drilling.

    M.

  • It’s a true TT. Possibly, it’s all under the paving. 

  • Hmm loop tests will show it I suppose. Less than a few ohms it is not simply TT. more than 100 and it was supposed to be TT but perhaps the driveway chaps chopped the cable.

    I guess it all depends on your appetite for hassle.

    I'm not going to mention RCD types ;-)

    Mike.

  • I’m feeling pretty comfortable with RCD types these days, even my own house has type A RCBOs. When I have an EV charger I’ll choose one with RDCDD to avoid silliness. I’ve even got one of the surge thingamagigs and just looking forward to being able to afford AFDDs without remortgaging the house!

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  • I’m feeling pretty comfortable with RCD types these days, even my own house has type A RCBOs. When I have an EV charger I’ll choose one with RDCDD to avoid silliness. I’ve even got one of the surge thingamagigs and just looking forward to being able to afford AFDDs without remortgaging the house!

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